A wedge bulb is a lighting device widely used in electric devices and mechanical devices including vehicles. Referring to FIG. 6, a conventional wedge bulb 4 includes a light emitting element 41 to emit light upon receiving power, and a connector 42 integrally provided at a lower end of the light emitting element 41 and configured to be inserted and fixed in an exclusive socket 200.
The connector 42 takes the form of a block and is provided at front and rear surfaces thereof with wedge shaped protrusions 421. The wedge shaped protrusions 421 serve to allow the connector 42 to be caught by a lower region of the socket 200, thereby preventing the wedge bulb 4 from being excessively inserted into the socket 200 beyond a predetermined depth. Also, a pair of electric terminals 43 is provided at the front and rear surfaces of the connector 42 to apply power to the light emitting element 41.
The socket 200 to receive the connector 42 therein is provided at an inner surface thereof with elastic terminals 210. The elastic terminals 210 are electrically conductively connectable to the respective electric terminals 43 and act to elastically press the connector 42.
More specifically, each of the elastic terminals 210 includes a terminal body 211 fixed to the socket 200, and an elastic ground piece 212 protruding from the terminal body 211.
In this case, a pair of the elastic ground pieces 212 is arranged to press a lower end of the connector 42 of the wedge bulb 4 from the front and rear sides thereof. In addition, additional press pieces 220 are used to elastically press an upper end of the connector 42 from the front and rear sides thereof. With cooperation of the elastic ground pieces 212 and the press pieces 220, the wedge bulb 4 may be fixed in the socket 200 without a risk of separation while achieving electrical connection between the electric terminals 43 and the elastic terminals 210.
However, since the above described conventional wedge bulb socket 200 holds the wedge bulb 4 by elastically pressing the lower end of the connector 42 of the wedge bulb 4, the electrical connection may become unstable due to, e.g., vibration of a mechanical device.
Specifically, the wedge bulb 4 is conventionally made of heavy glass, the light emitting element 41 protruding outward from the socket 200 has a large volume, and the connector 42 protrudes from the light emitting element 41. Therefore, the center of gravity of the wedge bulb 4 is located at the light emitting element 41, causing the wedge bulb 4 to vibrate easily relative to the socket 200 during vibration of a mechanical device, such as a vehicle, etc.
In addition, the elastic terminals 210 to elastically press the lower end of the connector 42 are arranged to press positions of the connector 42 distant from the center of gravity of the wedge bulb 4. This arrangement is disadvantageous in terms of maintenance of sufficient coupling between the wedge bulb 4 and the socket 200 during vibration of the wedge bulb 4.
The above described conventional wedge bulb socket may cause unstable connection between the electric terminals of the wedge bulb and the elastic ground pieces thereof due to vibration of the wedge bulb, thereby suffering from arcing due to defective electrical connection and burning of the electric terminals and the elastic ground pieces due to heat resulting from arcing.